Labels may be in any number of sizes or shapes, but may generally fall into two categories. One category is the wrap-around label in which the leading edge of the label is initially tacked with adhesive to a three dimensional object, such as a container or other product or product packaging of any shape. The label is then wrapped around the object so that the trailing edge of the label overlaps and is adhesively secured to the label itself. The other category encompasses label applications in which both the leading and trailing edges of the label are affixed directly to the object.
In general, adhesive has been applied to the labels via a wheel coater. Wheel coaters contain an open reservoir for holding the adhesive. A rotating wheel receives a coating of adhesive, which in turn is transferred to the label in a contact operation. Typically, a container, such as a bottle, can or other type of container or object moves along a conveyor and a paper or plastic label is secured to the outer surface of the container or object during a high speed production operation. For example, many production lines run at between 250 and 1400 label applying operations per minute.
There remain several challenges associated with using wheel coaters to apply adhesive to labels or three-dimensional objects such as containers. For example, wheel coaters can limit line speed increases because the reservoir of adhesive is subject to contamination from outside sources as well as from char and curing. Additionally, small changes in the contour of the container or object may result in improper coating of the label, resulting in unacceptable adhesion or appearance. Wheel coaters are therefore not particularly suited for applying adhesive to containers or bottles having grooves and ridges. Wheel coaters are often high maintenance components, requiring substantial down time and cost. Because wheel coaters rely on contacting the substrate to transfer the adhesive, precise alignment of the wheel is required. As the surface of the vacuum wheel carrying the labels wears or any of the associated components become misaligned, the efficiency of the labeling operation is negatively impacted. Sometimes frequent component maintenance or adjustment may be required as a result. Finally, the amount of adhesive applied by wheel coaters cannot be easily or accurately adjusted over a wide operating range. This type of adjustment capability can be important, for example, to ensure consistent adhesive coating weight application even as production line speeds change.
Labeling apparatus may come in several different forms, however, two different forms are known as cut and stacked labeling apparatus and roll-fed labeling apparatus. The latter type may also be referred to as reel-fed apparatus. In each of these cases, adhesive is either applied to the label or to the object or container, or both. The label is picked off of a label delivery mechanism, such as a magazine feeder of cut and stacked labels, or a vacuum wheel which takes labels from a reel or roll and holds the label to the vacuum wheel with negative pressure. The labels in a roll-fed apparatus may be cut apart from one another before applied to the vacuum wheel or while on the vacuum wheel. Wheel coaters have been traditionally used for both cut and stack and roll-fed labeling operation. Further information on reel-fed labeling can be found in the “Krones Contiroll Reel-Fed Labeling,” by Krones A G, dated July 2003, the disclosure is expressly incorporated by reference herein in its entirety. In addition, further information on wrap-around labeling can be found in “Krones Canmatic Wrap-Around Labeling,” by Krones A G, dated Jun. 2001.
The securement of the label to a bottle or container, for example, must be of such a quality that the label can withstand the various conditions that may be later experienced by the container or bottle during its shipping, storage, and use subsequent to the product packaging or filling operation. For example, with bottles of carbonated beverages, the label must withstand the expansion of the bottle due to the carbonation of the beverage and, for example, additional expansion and contraction during shipping and storage operations in which the temperatures of the product may widely vary. Furthermore, and just as important, the label must also be aesthetically pleasing. This means that the exposed edge of the label should not readily dog ear, become detached, have exposed adhesive or large amounts of adhesive forming lumps underneath the label.
There is a need for a manner of applying adhesive to either labels or containers, or both, in which the adhesive may be applied in a non-contact fashion, but also with lower needs for maintenance, and good adhesive coverage, while at the same time using a minimum amount of adhesive necessary to produce a strong attachment of the label to the container. In addition, there is a need for increased control over the amount of adhesive that is applied. There is also the need to reduce or eliminate frequent adjustments to the dispensing system as is necessary in wheel systems, as well as the ability to provide precision which is not possible with wheel coater systems. There is also the need to increase throughput in order to attach labels at faster speeds and to provide systems and methods that allow adjustment of adhesive coating weights over wide ranges.